Liquid phase preparation of 2-H-2-oxazolines and 2-substituted-2-oxazolines

Abstract

2-H-2-Oxazolines are prepared by contacting in liquid phase a N-(β-hydroxyalkyl)formamide with a small but catalytic amount of an inorganic zinc salt at elevated temperatures. Similarly, 2-substituted-2-oxazolines are prepared by contacting N-(2-hydroxyalkyl)carboxamides with a small but catalytic amount of an inorganic zinc salt. As an example, 2-H-2-oxazoline was prepared in approximately 72 percent yield by warming a mixture of N-(β-hydroxyethyl)formamide with a catalytic amount of zinc chloride at a temperature of from 180° C. to 185° C./50 mm Hg for 2.2 hours. In this reaction, the desired oxazoline product was recovered as a codistillate with water during the course of the reaction.

What is claimed is: 
     
       1. A cyclodehydration process for making a 2-R-2-oxazoline wherein R is hydrogen, a hydrocarbyl or an inertly-substituted hydrocarbyl, which comprises the steps of reacting by contacting in liquid phase, an N-(2-hydroxyalkyl)carboxamide corresponding to the formula: ##STR3## wherein R is as defined above, or a carboxylic acid/amine salt precursor of said N-(2-hydroxyethyl)carboxamide with a small but catalytic amount of an inorganic zinc salt of sulfuric, nitric, hydrochloric, hydrobromic, hydroiodic, phosphoric or hypophosphorous acid. 
     
     
       2. The process defined by claim 1 wherein R is hydrogen, methyl, ethyl, or phenyl. 
     
     
       3. The process defined by claim 2 wherein R is methyl or ethyl. 
     
     
       4. The process defined by claim 1 wherein said catalyst is charged in amounts of from about 0.005 to about 0.4 mole of inorganic zinc salt per mole of carboxamide reactant. 
     
     
       5. The process defined by claim 1 wherein said catalyst is zinc chloride or zinc sulfate. 
     
     
       6. The process defined by claim 1 wherein the process is conducted under conditions of temperature and pressure such that the 2-substituted-2-oxazoline product is removed from the reaction mixture as a volatile gas essentially as it is formed. 
     
     
       7. The process defined by claim 6 wherein said catalyst is zinc chloride, zinc sulfate or zinc iodide and wherein said carboxamide is N-(2-hydroxyethyl)-propionamide. 
     
     
       8. The process defined by claim 7 wherein said catalyst is charged in amounts of from about 0.005 to about 0.4 mole of inorganic zinc salt per mole of carboxamide reactant.